/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
 *
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 *
 *
 *
 *
 */

package java.lang.invoke;

import sun.invoke.util.VerifyAccess;
import java.lang.invoke.LambdaForm.Name;

import sun.invoke.util.Wrapper;

import java.io.*;
import java.util.*;

import jdk.internal.org.objectweb.asm.*;

import java.lang.reflect.*;
import static java.lang.invoke.MethodHandleStatics.*;
import static java.lang.invoke.MethodHandleNatives.Constants.*;
import sun.invoke.util.VerifyType;
import sun.reflect.misc.ReflectUtil;

/**
 * Code generation backend for LambdaForm.
 * <p>
 * @author John Rose, JSR 292 EG
 */
class InvokerBytecodeGenerator {
    /** Define class names for convenience. */
    private static final String MH = "java/lang/invoke/MethodHandle";
    private static final String MHI = "java/lang/invoke/MethodHandleImpl";
    private static final String LF = "java/lang/invoke/LambdaForm";
    private static final String LFN = "java/lang/invoke/LambdaForm$Name";
    private static final String CLS = "java/lang/Class";
    private static final String OBJ = "java/lang/Object";
    private static final String OBJARY = "[Ljava/lang/Object;";

    private static final String LF_SIG = "L" + LF + ";";
    private static final String LFN_SIG = "L" + LFN + ";";
    private static final String LL_SIG = "(L" + OBJ + ";)L" + OBJ + ";";
    private static final String CLL_SIG = "(L" + CLS + ";L" + OBJ + ";)L" + OBJ + ";";

    /** Name of its super class*/
    private static final String superName = LF;

    /** Name of new class */
    private final String className;

    /** Name of the source file (for stack trace printing). */
    private final String sourceFile;

    private final LambdaForm lambdaForm;
    private final String invokerName;
    private final MethodType invokerType;
    private final int[] localsMap;

    /** ASM bytecode generation. */
    private ClassWriter cw;
    private MethodVisitor mv;

    private static final MemberName.Factory MEMBERNAME_FACTORY = MemberName.getFactory();
    private static final Class<?> HOST_CLASS = LambdaForm.class;

    private InvokerBytecodeGenerator(LambdaForm lambdaForm, int localsMapSize, String className, String invokerName, MethodType invokerType) {
        if (invokerName.contains(".")) {
            int p = invokerName.indexOf(".");
            className = invokerName.substring(0, p);
            invokerName = invokerName.substring(p + 1);
        }
        if (DUMP_CLASS_FILES) {
            className = makeDumpableClassName(className);
        }
        this.className = superName + "$" + className;
        this.sourceFile = "LambdaForm$" + className;
        this.lambdaForm = lambdaForm;
        this.invokerName = invokerName;
        this.invokerType = invokerType;
        this.localsMap = new int[localsMapSize];
    }

    private InvokerBytecodeGenerator(String className, String invokerName, MethodType invokerType) {
        this(null, invokerType.parameterCount(), className, invokerName, invokerType);
        // Create an array to map name indexes to locals indexes.
        for (int i = 0; i < localsMap.length; i++) {
            localsMap[i] = invokerType.parameterSlotCount() - invokerType.parameterSlotDepth(i);
        }
    }

    private InvokerBytecodeGenerator(String className, LambdaForm form, MethodType invokerType) {
        this(form, form.names.length, className, form.debugName, invokerType);
        // Create an array to map name indexes to locals indexes.
        Name[] names = form.names;
        for (int i = 0, index = 0; i < localsMap.length; i++) {
            localsMap[i] = index;
            index += Wrapper.forBasicType(names[i].type).stackSlots();
        }
    }

    /** instance counters for dumped classes */
    private final static HashMap<String, Integer> DUMP_CLASS_FILES_COUNTERS;
    /** debugging flag for saving generated class files */
    private final static File DUMP_CLASS_FILES_DIR;

    static {
        if (DUMP_CLASS_FILES) {
            DUMP_CLASS_FILES_COUNTERS = new HashMap<>();
            try {
                File dumpDir = new File("DUMP_CLASS_FILES");
                if (!dumpDir.exists()) {
                    dumpDir.mkdirs();
                }
                DUMP_CLASS_FILES_DIR = dumpDir;
                System.out.println("Dumping class files to " + DUMP_CLASS_FILES_DIR + "/...");
            } catch (Exception e) {
                throw newInternalError(e);
            }
        } else {
            DUMP_CLASS_FILES_COUNTERS = null;
            DUMP_CLASS_FILES_DIR = null;
        }
    }

    static void maybeDump(final String className, final byte[] classFile) {
        if (DUMP_CLASS_FILES) {
            System.out.println("dump: " + className);
            java.security.AccessController.doPrivileged(new java.security.PrivilegedAction<Void>() {
                public Void run() {
                    try {
                        String dumpName = className;
                        //dumpName = dumpName.replace('/', '-');
                        File dumpFile = new File(DUMP_CLASS_FILES_DIR, dumpName + ".class");
                        dumpFile.getParentFile().mkdirs();
                        FileOutputStream file = new FileOutputStream(dumpFile);
                        file.write(classFile);
                        file.close();
                        return null;
                    } catch (IOException ex) {
                        throw newInternalError(ex);
                    }
                }
            });
        }

    }

    private static String makeDumpableClassName(String className) {
        Integer ctr;
        synchronized (DUMP_CLASS_FILES_COUNTERS) {
            ctr = DUMP_CLASS_FILES_COUNTERS.get(className);
            if (ctr == null)
                ctr = 0;
            DUMP_CLASS_FILES_COUNTERS.put(className, ctr + 1);
        }
        String sfx = ctr.toString();
        while (sfx.length() < 3)
            sfx = "0" + sfx;
        className += sfx;
        return className;
    }

    class CpPatch {
        final int index;
        final String placeholder;
        final Object value;

        CpPatch(int index, String placeholder, Object value) {
            this.index = index;
            this.placeholder = placeholder;
            this.value = value;
        }

        public String toString() {
            return "CpPatch/index=" + index + ",placeholder=" + placeholder + ",value=" + value;
        }
    }

    Map<Object, CpPatch> cpPatches = new HashMap<>();

    int cph = 0; // for counting constant placeholders

    String constantPlaceholder(Object arg) {
        String cpPlaceholder = "CONSTANT_PLACEHOLDER_" + cph++;
        if (DUMP_CLASS_FILES)
            cpPlaceholder += " <<" + arg.toString() + ">>"; // debugging aid
        if (cpPatches.containsKey(cpPlaceholder)) {
            throw new InternalError("observed CP placeholder twice: " + cpPlaceholder);
        }
        // insert placeholder in CP and remember the patch
        int index = cw.newConst((Object) cpPlaceholder); // TODO check if aready in the constant pool
        cpPatches.put(cpPlaceholder, new CpPatch(index, cpPlaceholder, arg));
        return cpPlaceholder;
    }

    Object[] cpPatches(byte[] classFile) {
        int size = getConstantPoolSize(classFile);
        Object[] res = new Object[size];
        for (CpPatch p : cpPatches.values()) {
            if (p.index >= size)
                throw new InternalError("in cpool[" + size + "]: " + p + "\n" + Arrays.toString(Arrays.copyOf(classFile, 20)));
            res[p.index] = p.value;
        }
        return res;
    }

    /**
     * Extract the number of constant pool entries from a given class file.
     *
     * @param classFile the bytes of the class file in question.
     * @return the number of entries in the constant pool.
     */
    private static int getConstantPoolSize(byte[] classFile) {
        // The first few bytes:
        // u4 magic;
        // u2 minor_version;
        // u2 major_version;
        // u2 constant_pool_count;
        return ((classFile[8] & 0xFF) << 8) | (classFile[9] & 0xFF);
    }

    /**
     * Extract the MemberName of a newly-defined method.
     */
    private MemberName loadMethod(byte[] classFile) {
        Class<?> invokerClass = loadAndInitializeInvokerClass(classFile, cpPatches(classFile));
        return resolveInvokerMember(invokerClass, invokerName, invokerType);
    }

    /**
     * Define a given class as anonymous class in the runtime system.
     */
    private static Class<?> loadAndInitializeInvokerClass(byte[] classBytes, Object[] patches) {
        Class<?> invokerClass = UNSAFE.defineAnonymousClass(HOST_CLASS, classBytes, patches);
        UNSAFE.ensureClassInitialized(invokerClass); // Make sure the class is initialized; VM might complain.
        return invokerClass;
    }

    private static MemberName resolveInvokerMember(Class<?> invokerClass, String name, MethodType type) {
        MemberName member = new MemberName(invokerClass, name, type, REF_invokeStatic);
        //System.out.println("resolveInvokerMember => "+member);
        //for (Method m : invokerClass.getDeclaredMethods())  System.out.println("  "+m);
        try {
            member = MEMBERNAME_FACTORY.resolveOrFail(REF_invokeStatic, member, HOST_CLASS, ReflectiveOperationException.class);
        } catch (ReflectiveOperationException e) {
            throw newInternalError(e);
        }
        //System.out.println("resolveInvokerMember => "+member);
        return member;
    }

    /**
     * Set up class file generation.
     */
    private void classFilePrologue() {
        final int NOT_ACC_PUBLIC = 0; // not ACC_PUBLIC
        cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);
        cw.visit(Opcodes.V1_8, NOT_ACC_PUBLIC + Opcodes.ACC_FINAL + Opcodes.ACC_SUPER, className, null, superName, null);
        cw.visitSource(sourceFile, null);

        String invokerDesc = invokerType.toMethodDescriptorString();
        mv = cw.visitMethod(Opcodes.ACC_STATIC, invokerName, invokerDesc, null, null);
    }

    /**
     * Tear down class file generation.
     */
    private void classFileEpilogue() {
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }

    /*
     * Low-level emit helpers.
     */
    private void emitConst(Object con) {
        if (con == null) {
            mv.visitInsn(Opcodes.ACONST_NULL);
            return;
        }
        if (con instanceof Integer) {
            emitIconstInsn((int) con);
            return;
        }
        if (con instanceof Long) {
            long x = (long) con;
            if (x == (short) x) {
                emitIconstInsn((int) x);
                mv.visitInsn(Opcodes.I2L);
                return;
            }
        }
        if (con instanceof Float) {
            float x = (float) con;
            if (x == (short) x) {
                emitIconstInsn((int) x);
                mv.visitInsn(Opcodes.I2F);
                return;
            }
        }
        if (con instanceof Double) {
            double x = (double) con;
            if (x == (short) x) {
                emitIconstInsn((int) x);
                mv.visitInsn(Opcodes.I2D);
                return;
            }
        }
        if (con instanceof Boolean) {
            emitIconstInsn((boolean) con ? 1 : 0);
            return;
        }
        // fall through:
        mv.visitLdcInsn(con);
    }

    private void emitIconstInsn(int i) {
        int opcode;
        switch (i) {
            case 0:
                opcode = Opcodes.ICONST_0;
                break;
            case 1:
                opcode = Opcodes.ICONST_1;
                break;
            case 2:
                opcode = Opcodes.ICONST_2;
                break;
            case 3:
                opcode = Opcodes.ICONST_3;
                break;
            case 4:
                opcode = Opcodes.ICONST_4;
                break;
            case 5:
                opcode = Opcodes.ICONST_5;
                break;
            default:
                if (i == (byte) i) {
                    mv.visitIntInsn(Opcodes.BIPUSH, i & 0xFF);
                } else if (i == (short) i) {
                    mv.visitIntInsn(Opcodes.SIPUSH, (char) i);
                } else {
                    mv.visitLdcInsn(i);
                }
                return;
        }
        mv.visitInsn(opcode);
    }

    /*
     * NOTE: These load/store methods use the localsMap to find the correct index!
     */
    private void emitLoadInsn(char type, int index) {
        int opcode;
        switch (type) {
            case 'I':
                opcode = Opcodes.ILOAD;
                break;
            case 'J':
                opcode = Opcodes.LLOAD;
                break;
            case 'F':
                opcode = Opcodes.FLOAD;
                break;
            case 'D':
                opcode = Opcodes.DLOAD;
                break;
            case 'L':
                opcode = Opcodes.ALOAD;
                break;
            default:
                throw new InternalError("unknown type: " + type);
        }
        mv.visitVarInsn(opcode, localsMap[index]);
    }

    private void emitAloadInsn(int index) {
        emitLoadInsn('L', index);
    }

    private void emitStoreInsn(char type, int index) {
        int opcode;
        switch (type) {
            case 'I':
                opcode = Opcodes.ISTORE;
                break;
            case 'J':
                opcode = Opcodes.LSTORE;
                break;
            case 'F':
                opcode = Opcodes.FSTORE;
                break;
            case 'D':
                opcode = Opcodes.DSTORE;
                break;
            case 'L':
                opcode = Opcodes.ASTORE;
                break;
            default:
                throw new InternalError("unknown type: " + type);
        }
        mv.visitVarInsn(opcode, localsMap[index]);
    }

    private void emitAstoreInsn(int index) {
        emitStoreInsn('L', index);
    }

    /**
     * Emit a boxing call.
     *
     * @param type primitive type class to box.
     */
    private void emitBoxing(Class<?> type) {
        Wrapper wrapper = Wrapper.forPrimitiveType(type);
        String owner = "java/lang/" + wrapper.wrapperType().getSimpleName();
        String name = "valueOf";
        String desc = "(" + wrapper.basicTypeChar() + ")L" + owner + ";";
        mv.visitMethodInsn(Opcodes.INVOKESTATIC, owner, name, desc);
    }

    /**
     * Emit an unboxing call (plus preceding checkcast).
     *
     * @param type wrapper type class to unbox.
     */
    private void emitUnboxing(Class<?> type) {
        Wrapper wrapper = Wrapper.forWrapperType(type);
        String owner = "java/lang/" + wrapper.wrapperType().getSimpleName();
        String name = wrapper.primitiveSimpleName() + "Value";
        String desc = "()" + wrapper.basicTypeChar();
        mv.visitTypeInsn(Opcodes.CHECKCAST, owner);
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, owner, name, desc);
    }

    /**
     * Emit an implicit conversion.
     *
     * @param ptype type of value present on stack
     * @param pclass type of value required on stack
     */
    private void emitImplicitConversion(char ptype, Class<?> pclass) {
        switch (ptype) {
            case 'L':
                if (VerifyType.isNullConversion(Object.class, pclass))
                    return;
                if (isStaticallyNameable(pclass)) {
                    mv.visitTypeInsn(Opcodes.CHECKCAST, getInternalName(pclass));
                } else {
                    mv.visitLdcInsn(constantPlaceholder(pclass));
                    mv.visitTypeInsn(Opcodes.CHECKCAST, CLS);
                    mv.visitInsn(Opcodes.SWAP);
                    mv.visitMethodInsn(Opcodes.INVOKESTATIC, MHI, "castReference", CLL_SIG);
                    if (pclass.isArray())
                        mv.visitTypeInsn(Opcodes.CHECKCAST, OBJARY);
                }
                return;
            case 'I':
                if (!VerifyType.isNullConversion(int.class, pclass))
                    emitPrimCast(ptype, Wrapper.basicTypeChar(pclass));
                return;
            case 'J':
                assert (pclass == long.class);
                return;
            case 'F':
                assert (pclass == float.class);
                return;
            case 'D':
                assert (pclass == double.class);
                return;
        }
        throw new InternalError("bad implicit conversion: tc=" + ptype + ": " + pclass);
    }

    /**
     * Emits an actual return instruction conforming to the given return type.
     */
    private void emitReturnInsn(Class<?> type) {
        int opcode;
        switch (Wrapper.basicTypeChar(type)) {
            case 'I':
                opcode = Opcodes.IRETURN;
                break;
            case 'J':
                opcode = Opcodes.LRETURN;
                break;
            case 'F':
                opcode = Opcodes.FRETURN;
                break;
            case 'D':
                opcode = Opcodes.DRETURN;
                break;
            case 'L':
                opcode = Opcodes.ARETURN;
                break;
            case 'V':
                opcode = Opcodes.RETURN;
                break;
            default:
                throw new InternalError("unknown return type: " + type);
        }
        mv.visitInsn(opcode);
    }

    private static String getInternalName(Class<?> c) {
        assert (VerifyAccess.isTypeVisible(c, Object.class));
        return c.getName().replace('.', '/');
    }

    /**
     * Generate customized bytecode for a given LambdaForm.
     */
    static MemberName generateCustomizedCode(LambdaForm form, MethodType invokerType) {
        InvokerBytecodeGenerator g = new InvokerBytecodeGenerator("MH", form, invokerType);
        return g.loadMethod(g.generateCustomizedCodeBytes());
    }

    /**
     * Generate an invoker method for the passed {@link LambdaForm}.
     */
    private byte[] generateCustomizedCodeBytes() {
        classFilePrologue();

        // Suppress this method in backtraces displayed to the user.
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);

        // Mark this method as a compiled LambdaForm
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Compiled;", true);

        // Force inlining of this invoker method.
        mv.visitAnnotation("Ljava/lang/invoke/ForceInline;", true);

        // iterate over the form's names, generating bytecode instructions for each
        // start iterating at the first name following the arguments
        for (int i = lambdaForm.arity; i < lambdaForm.names.length; i++) {
            Name name = lambdaForm.names[i];
            MemberName member = name.function.member();

            if (isSelectAlternative(i)) {
                emitSelectAlternative(name, lambdaForm.names[i + 1]);
                i++; // skip MH.invokeBasic of the selectAlternative result
            } else if (isGuardWithCatch(i)) {
                emitGuardWithCatch(i);
                i = i + 2; // Jump to the end of GWC idiom
            } else if (isStaticallyInvocable(member)) {
                emitStaticInvoke(member, name);
            } else {
                emitInvoke(name);
            }

            // Update cached form name's info in case an intrinsic spanning multiple names was encountered.
            name = lambdaForm.names[i];
            member = name.function.member();

            // store the result from evaluating to the target name in a local if required
            // (if this is the last value, i.e., the one that is going to be returned,
            // avoid store/load/return and just return)
            if (i == lambdaForm.names.length - 1 && i == lambdaForm.result) {
                // return value - do nothing
            } else if (name.type != 'V') {
                // non-void: actually assign
                emitStoreInsn(name.type, name.index());
            }
        }

        // return statement
        emitReturn();

        classFileEpilogue();
        bogusMethod(lambdaForm);

        final byte[] classFile = cw.toByteArray();
        maybeDump(className, classFile);
        return classFile;
    }

    /**
     * Emit an invoke for the given name.
     */
    void emitInvoke(Name name) {
        if (true) {
            // push receiver
            MethodHandle target = name.function.resolvedHandle;
            assert (target != null) : name.exprString();
            mv.visitLdcInsn(constantPlaceholder(target));
            mv.visitTypeInsn(Opcodes.CHECKCAST, MH);
        } else {
            // load receiver
            emitAloadInsn(0);
            mv.visitTypeInsn(Opcodes.CHECKCAST, MH);
            mv.visitFieldInsn(Opcodes.GETFIELD, MH, "form", LF_SIG);
            mv.visitFieldInsn(Opcodes.GETFIELD, LF, "names", LFN_SIG);
            // TODO more to come
        }

        // push arguments
        for (int i = 0; i < name.arguments.length; i++) {
            emitPushArgument(name, i);
        }

        // invocation
        MethodType type = name.function.methodType();
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, MH, "invokeBasic", type.basicType().toMethodDescriptorString());
    }

    static private Class<?>[] STATICALLY_INVOCABLE_PACKAGES = {
            // Sample classes from each package we are willing to bind to statically:
            java.lang.Object.class, java.util.Arrays.class, sun.misc.Unsafe.class
            //MethodHandle.class already covered
    };

    static boolean isStaticallyInvocable(MemberName member) {
        if (member == null)
            return false;
        if (member.isConstructor())
            return false;
        Class<?> cls = member.getDeclaringClass();
        if (cls.isArray() || cls.isPrimitive())
            return false; // FIXME
        if (cls.isAnonymousClass() || cls.isLocalClass())
            return false; // inner class of some sort
        if (cls.getClassLoader() != MethodHandle.class.getClassLoader())
            return false; // not on BCP
        if (ReflectUtil.isVMAnonymousClass(cls)) // FIXME: switch to supported API once it is added
            return false;
        MethodType mtype = member.getMethodOrFieldType();
        if (!isStaticallyNameable(mtype.returnType()))
            return false;
        for (Class<?> ptype : mtype.parameterArray())
            if (!isStaticallyNameable(ptype))
                return false;
        if (!member.isPrivate() && VerifyAccess.isSamePackage(MethodHandle.class, cls))
            return true; // in java.lang.invoke package
        if (member.isPublic() && isStaticallyNameable(cls))
            return true;
        return false;
    }

    static boolean isStaticallyNameable(Class<?> cls) {
        while (cls.isArray())
            cls = cls.getComponentType();
        if (cls.isPrimitive())
            return true; // int[].class, for example
        if (ReflectUtil.isVMAnonymousClass(cls)) // FIXME: switch to supported API once it is added
            return false;
        // could use VerifyAccess.isClassAccessible but the following is a safe approximation
        if (cls.getClassLoader() != Object.class.getClassLoader())
            return false;
        if (VerifyAccess.isSamePackage(MethodHandle.class, cls))
            return true;
        if (!Modifier.isPublic(cls.getModifiers()))
            return false;
        for (Class<?> pkgcls : STATICALLY_INVOCABLE_PACKAGES) {
            if (VerifyAccess.isSamePackage(pkgcls, cls))
                return true;
        }
        return false;
    }

    /**
     * Emit an invoke for the given name, using the MemberName directly.
     */
    void emitStaticInvoke(MemberName member, Name name) {
        assert (member.equals(name.function.member()));
        String cname = getInternalName(member.getDeclaringClass());
        String mname = member.getName();
        String mtype;
        byte refKind = member.getReferenceKind();
        if (refKind == REF_invokeSpecial) {
            // in order to pass the verifier, we need to convert this to invokevirtual in all cases
            assert (member.canBeStaticallyBound()) : member;
            refKind = REF_invokeVirtual;
        }

        if (member.getDeclaringClass().isInterface() && refKind == REF_invokeVirtual) {
            // Methods from Object declared in an interface can be resolved by JVM to invokevirtual kind.
            // Need to convert it back to invokeinterface to pass verification and make the invocation works as expected.
            refKind = REF_invokeInterface;
        }

        // push arguments
        for (int i = 0; i < name.arguments.length; i++) {
            emitPushArgument(name, i);
        }

        // invocation
        if (member.isMethod()) {
            mtype = member.getMethodType().toMethodDescriptorString();
            mv.visitMethodInsn(refKindOpcode(refKind), cname, mname, mtype, member.getDeclaringClass().isInterface());
        } else {
            mtype = MethodType.toFieldDescriptorString(member.getFieldType());
            mv.visitFieldInsn(refKindOpcode(refKind), cname, mname, mtype);
        }
    }

    int refKindOpcode(byte refKind) {
        switch (refKind) {
            case REF_invokeVirtual:
                return Opcodes.INVOKEVIRTUAL;
            case REF_invokeStatic:
                return Opcodes.INVOKESTATIC;
            case REF_invokeSpecial:
                return Opcodes.INVOKESPECIAL;
            case REF_invokeInterface:
                return Opcodes.INVOKEINTERFACE;
            case REF_getField:
                return Opcodes.GETFIELD;
            case REF_putField:
                return Opcodes.PUTFIELD;
            case REF_getStatic:
                return Opcodes.GETSTATIC;
            case REF_putStatic:
                return Opcodes.PUTSTATIC;
        }
        throw new InternalError("refKind=" + refKind);
    }

    /**
     * Check if MemberName is a call to a method named {@code name} in class {@code declaredClass}.
     */
    private boolean memberRefersTo(MemberName member, Class<?> declaringClass, String name) {
        return member != null && member.getDeclaringClass() == declaringClass && member.getName().equals(name);
    }

    private boolean nameRefersTo(Name name, Class<?> declaringClass, String methodName) {
        return name.function != null && memberRefersTo(name.function.member(), declaringClass, methodName);
    }

    /**
     * Check if MemberName is a call to MethodHandle.invokeBasic.
     */
    private boolean isInvokeBasic(Name name) {
        if (name.function == null)
            return false;
        if (name.arguments.length < 1)
            return false; // must have MH argument
        MemberName member = name.function.member();
        return memberRefersTo(member, MethodHandle.class, "invokeBasic") && !member.isPublic() && !member.isStatic();
    }

    /**
     * Check if i-th name is a call to MethodHandleImpl.selectAlternative.
     */
    private boolean isSelectAlternative(int pos) {
        // selectAlternative idiom:
        //   t_{n}:L=MethodHandleImpl.selectAlternative(...)
        //   t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)
        if (pos + 1 >= lambdaForm.names.length)
            return false;
        Name name0 = lambdaForm.names[pos];
        Name name1 = lambdaForm.names[pos + 1];
        return nameRefersTo(name0, MethodHandleImpl.class, "selectAlternative") && isInvokeBasic(name1) && name1.lastUseIndex(name0) == 0 && // t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)
        lambdaForm.lastUseIndex(name0) == pos + 1; // t_{n} is local: used only in t_{n+1}
    }

    /**
     * Check if i-th name is a start of GuardWithCatch idiom.
     */
    private boolean isGuardWithCatch(int pos) {
        // GuardWithCatch idiom:
        //   t_{n}:L=MethodHandle.invokeBasic(...)
        //   t_{n+1}:L=MethodHandleImpl.guardWithCatch(*, *, *, t_{n});
        //   t_{n+2}:?=MethodHandle.invokeBasic(t_{n+1})
        if (pos + 2 >= lambdaForm.names.length)
            return false;
        Name name0 = lambdaForm.names[pos];
        Name name1 = lambdaForm.names[pos + 1];
        Name name2 = lambdaForm.names[pos + 2];
        return nameRefersTo(name1, MethodHandleImpl.class, "guardWithCatch") && isInvokeBasic(name0) && isInvokeBasic(name2) && name1.lastUseIndex(name0) == 3 && // t_{n+1}:L=MethodHandleImpl.guardWithCatch(*, *, *, t_{n});
        lambdaForm.lastUseIndex(name0) == pos + 1 && // t_{n} is local: used only in t_{n+1}
        name2.lastUseIndex(name1) == 1 && // t_{n+2}:?=MethodHandle.invokeBasic(t_{n+1})
        lambdaForm.lastUseIndex(name1) == pos + 2; // t_{n+1} is local: used only in t_{n+2}
    }

    /**
     * Emit bytecode for the selectAlternative idiom.
     *
     * The pattern looks like (Cf. MethodHandleImpl.makeGuardWithTest):
     * <blockquote><pre>{@code
     *   Lambda(a0:L,a1:I)=>{
     *     t2:I=foo.test(a1:I);
     *     t3:L=MethodHandleImpl.selectAlternative(t2:I,(MethodHandle(int)int),(MethodHandle(int)int));
     *     t4:I=MethodHandle.invokeBasic(t3:L,a1:I);t4:I}
     * }</pre></blockquote>
     */
    private void emitSelectAlternative(Name selectAlternativeName, Name invokeBasicName) {
        Name receiver = (Name) invokeBasicName.arguments[0];

        Label L_fallback = new Label();
        Label L_done = new Label();

        // load test result
        emitPushArgument(selectAlternativeName, 0);
        mv.visitInsn(Opcodes.ICONST_1);

        // if_icmpne L_fallback
        mv.visitJumpInsn(Opcodes.IF_ICMPNE, L_fallback);

        // invoke selectAlternativeName.arguments[1]
        emitPushArgument(selectAlternativeName, 1); // get 2nd argument of selectAlternative
        emitAstoreInsn(receiver.index()); // store the MH in the receiver slot
        emitInvoke(invokeBasicName);

        // goto L_done
        mv.visitJumpInsn(Opcodes.GOTO, L_done);

        // L_fallback:
        mv.visitLabel(L_fallback);

        // invoke selectAlternativeName.arguments[2]
        emitPushArgument(selectAlternativeName, 2); // get 3rd argument of selectAlternative
        emitAstoreInsn(receiver.index()); // store the MH in the receiver slot
        emitInvoke(invokeBasicName);

        // L_done:
        mv.visitLabel(L_done);
    }

    /**
      * Emit bytecode for the guardWithCatch idiom.
      *
      * The pattern looks like (Cf. MethodHandleImpl.makeGuardWithCatch):
      * <blockquote><pre>{@code
      *  guardWithCatch=Lambda(a0:L,a1:L,a2:L,a3:L,a4:L,a5:L,a6:L,a7:L)=>{
      *    t8:L=MethodHandle.invokeBasic(a4:L,a6:L,a7:L);
      *    t9:L=MethodHandleImpl.guardWithCatch(a1:L,a2:L,a3:L,t8:L);
      *   t10:I=MethodHandle.invokeBasic(a5:L,t9:L);t10:I}
      * }</pre></blockquote>
      *
      * It is compiled into bytecode equivalent of the following code:
      * <blockquote><pre>{@code
      *  try {
      *      return a1.invokeBasic(a6, a7);
      *  } catch (Throwable e) {
      *      if (!a2.isInstance(e)) throw e;
      *      return a3.invokeBasic(ex, a6, a7);
      *  }}
      */
    private void emitGuardWithCatch(int pos) {
        Name args = lambdaForm.names[pos];
        Name invoker = lambdaForm.names[pos + 1];
        Name result = lambdaForm.names[pos + 2];

        Label L_startBlock = new Label();
        Label L_endBlock = new Label();
        Label L_handler = new Label();
        Label L_done = new Label();

        Class<?> returnType = result.function.resolvedHandle.type().returnType();
        MethodType type = args.function.resolvedHandle.type().dropParameterTypes(0, 1).changeReturnType(returnType);

        mv.visitTryCatchBlock(L_startBlock, L_endBlock, L_handler, "java/lang/Throwable");

        // Normal case
        mv.visitLabel(L_startBlock);
        // load target
        emitPushArgument(invoker, 0);
        emitPushArguments(args, 1); // skip 1st argument: method handle
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, MH, "invokeBasic", type.basicType().toMethodDescriptorString(), false);
        mv.visitLabel(L_endBlock);
        mv.visitJumpInsn(Opcodes.GOTO, L_done);

        // Exceptional case
        mv.visitLabel(L_handler);

        // Check exception's type
        mv.visitInsn(Opcodes.DUP);
        // load exception class
        emitPushArgument(invoker, 1);
        mv.visitInsn(Opcodes.SWAP);
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Class", "isInstance", "(Ljava/lang/Object;)Z", false);
        Label L_rethrow = new Label();
        mv.visitJumpInsn(Opcodes.IFEQ, L_rethrow);

        // Invoke catcher
        // load catcher
        emitPushArgument(invoker, 2);
        mv.visitInsn(Opcodes.SWAP);
        emitPushArguments(args, 1); // skip 1st argument: method handle
        MethodType catcherType = type.insertParameterTypes(0, Throwable.class);
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, MH, "invokeBasic", catcherType.basicType().toMethodDescriptorString(), false);
        mv.visitJumpInsn(Opcodes.GOTO, L_done);

        mv.visitLabel(L_rethrow);
        mv.visitInsn(Opcodes.ATHROW);

        mv.visitLabel(L_done);
    }

    private void emitPushArguments(Name args, int start) {
        for (int i = start; i < args.arguments.length; i++) {
            emitPushArgument(args, i);
        }
    }

    private void emitPushArgument(Name name, int paramIndex) {
        Object arg = name.arguments[paramIndex];
        char ptype = name.function.parameterType(paramIndex);
        MethodType mtype = name.function.methodType();
        if (arg instanceof Name) {
            Name n = (Name) arg;
            emitLoadInsn(n.type, n.index());
            emitImplicitConversion(n.type, mtype.parameterType(paramIndex));
        } else if ((arg == null || arg instanceof String) && ptype == 'L') {
            emitConst(arg);
        } else {
            if (Wrapper.isWrapperType(arg.getClass()) && ptype != 'L') {
                emitConst(arg);
            } else {
                mv.visitLdcInsn(constantPlaceholder(arg));
                emitImplicitConversion('L', mtype.parameterType(paramIndex));
            }
        }
    }

    /**
     * Emits a return statement from a LF invoker. If required, the result type is cast to the correct return type.
     */
    private void emitReturn() {
        // return statement
        if (lambdaForm.result == -1) {
            // void
            mv.visitInsn(Opcodes.RETURN);
        } else {
            LambdaForm.Name rn = lambdaForm.names[lambdaForm.result];
            char rtype = Wrapper.basicTypeChar(invokerType.returnType());

            // put return value on the stack if it is not already there
            if (lambdaForm.result != lambdaForm.names.length - 1) {
                emitLoadInsn(rn.type, lambdaForm.result);
            }

            // potentially generate cast
            // rtype is the return type of the invoker - generated code must conform to this
            // rn.type is the type of the result Name in the LF
            if (rtype != rn.type) {
                // need cast
                if (rtype == 'L') {
                    // possibly cast the primitive to the correct type for boxing
                    char boxedType = Wrapper.forWrapperType(invokerType.returnType()).basicTypeChar();
                    if (boxedType != rn.type) {
                        emitPrimCast(rn.type, boxedType);
                    }
                    // cast primitive to reference ("boxing")
                    emitBoxing(invokerType.returnType());
                } else {
                    // to-primitive cast
                    if (rn.type != 'L') {
                        // prim-to-prim cast
                        emitPrimCast(rn.type, rtype);
                    } else {
                        // ref-to-prim cast ("unboxing")
                        throw new InternalError("no ref-to-prim (unboxing) casts supported right now");
                    }
                }
            }

            // generate actual return statement
            emitReturnInsn(invokerType.returnType());
        }
    }

    /**
     * Emit a type conversion bytecode casting from "from" to "to".
     */
    private void emitPrimCast(char from, char to) {
        // Here's how.
        // -   indicates forbidden
        // <-> indicates implicit
        //      to ----> boolean  byte     short    char     int      long     float    double
        // from boolean    <->        -        -        -        -        -        -        -
        //      byte        -       <->       i2s      i2c      <->      i2l      i2f      i2d
        //      short       -       i2b       <->      i2c      <->      i2l      i2f      i2d
        //      char        -       i2b       i2s      <->      <->      i2l      i2f      i2d
        //      int         -       i2b       i2s      i2c      <->      i2l      i2f      i2d
        //      long        -     l2i,i2b   l2i,i2s  l2i,i2c    l2i      <->      l2f      l2d
        //      float       -     f2i,i2b   f2i,i2s  f2i,i2c    f2i      f2l      <->      f2d
        //      double      -     d2i,i2b   d2i,i2s  d2i,i2c    d2i      d2l      d2f      <->
        if (from == to) {
            // no cast required, should be dead code anyway
            return;
        }
        Wrapper wfrom = Wrapper.forBasicType(from);
        Wrapper wto = Wrapper.forBasicType(to);
        if (wfrom.isSubwordOrInt()) {
            // cast from {byte,short,char,int} to anything
            emitI2X(to);
        } else {
            // cast from {long,float,double} to anything
            if (wto.isSubwordOrInt()) {
                // cast to {byte,short,char,int}
                emitX2I(from);
                if (wto.bitWidth() < 32) {
                    // targets other than int require another conversion
                    emitI2X(to);
                }
            } else {
                // cast to {long,float,double} - this is verbose
                boolean error = false;
                switch (from) {
                    case 'J':
                        if (to == 'F') {
                            mv.visitInsn(Opcodes.L2F);
                        } else if (to == 'D') {
                            mv.visitInsn(Opcodes.L2D);
                        } else
                            error = true;
                        break;
                    case 'F':
                        if (to == 'J') {
                            mv.visitInsn(Opcodes.F2L);
                        } else if (to == 'D') {
                            mv.visitInsn(Opcodes.F2D);
                        } else
                            error = true;
                        break;
                    case 'D':
                        if (to == 'J') {
                            mv.visitInsn(Opcodes.D2L);
                        } else if (to == 'F') {
                            mv.visitInsn(Opcodes.D2F);
                        } else
                            error = true;
                        break;
                    default:
                        error = true;
                        break;
                }
                if (error) {
                    throw new IllegalStateException("unhandled prim cast: " + from + "2" + to);
                }
            }
        }
    }

    private void emitI2X(char type) {
        switch (type) {
            case 'B':
                mv.visitInsn(Opcodes.I2B);
                break;
            case 'S':
                mv.visitInsn(Opcodes.I2S);
                break;
            case 'C':
                mv.visitInsn(Opcodes.I2C);
                break;
            case 'I':
                /* naught */ break;
            case 'J':
                mv.visitInsn(Opcodes.I2L);
                break;
            case 'F':
                mv.visitInsn(Opcodes.I2F);
                break;
            case 'D':
                mv.visitInsn(Opcodes.I2D);
                break;
            case 'Z':
                // For compatibility with ValueConversions and explicitCastArguments:
                mv.visitInsn(Opcodes.ICONST_1);
                mv.visitInsn(Opcodes.IAND);
                break;
            default:
                throw new InternalError("unknown type: " + type);
        }
    }

    private void emitX2I(char type) {
        switch (type) {
            case 'J':
                mv.visitInsn(Opcodes.L2I);
                break;
            case 'F':
                mv.visitInsn(Opcodes.F2I);
                break;
            case 'D':
                mv.visitInsn(Opcodes.D2I);
                break;
            default:
                throw new InternalError("unknown type: " + type);
        }
    }

    private static String basicTypeCharSignature(String prefix, MethodType type) {
        StringBuilder buf = new StringBuilder(prefix);
        for (Class<?> ptype : type.parameterList())
            buf.append(Wrapper.forBasicType(ptype).basicTypeChar());
        buf.append('_').append(Wrapper.forBasicType(type.returnType()).basicTypeChar());
        return buf.toString();
    }

    /**
     * Generate bytecode for a LambdaForm.vmentry which calls interpretWithArguments.
     */
    static MemberName generateLambdaFormInterpreterEntryPoint(String sig) {
        assert (LambdaForm.isValidSignature(sig));
        //System.out.println("generateExactInvoker "+sig);
        // compute method type
        // first parameter and return type
        char tret = LambdaForm.signatureReturn(sig);
        MethodType type = MethodType.methodType(LambdaForm.typeClass(tret), MethodHandle.class);
        // other parameter types
        int arity = LambdaForm.signatureArity(sig);
        for (int i = 1; i < arity; i++) {
            type = type.appendParameterTypes(LambdaForm.typeClass(sig.charAt(i)));
        }
        InvokerBytecodeGenerator g = new InvokerBytecodeGenerator("LFI", "interpret_" + tret, type);
        return g.loadMethod(g.generateLambdaFormInterpreterEntryPointBytes());
    }

    private byte[] generateLambdaFormInterpreterEntryPointBytes() {
        classFilePrologue();

        // Suppress this method in backtraces displayed to the user.
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);

        // Don't inline the interpreter entry.
        mv.visitAnnotation("Ljava/lang/invoke/DontInline;", true);

        // create parameter array
        emitIconstInsn(invokerType.parameterCount());
        mv.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");

        // fill parameter array
        for (int i = 0; i < invokerType.parameterCount(); i++) {
            Class<?> ptype = invokerType.parameterType(i);
            mv.visitInsn(Opcodes.DUP);
            emitIconstInsn(i);
            emitLoadInsn(Wrapper.basicTypeChar(ptype), i);
            // box if primitive type
            if (ptype.isPrimitive()) {
                emitBoxing(ptype);
            }
            mv.visitInsn(Opcodes.AASTORE);
        }
        // invoke
        emitAloadInsn(0);
        mv.visitFieldInsn(Opcodes.GETFIELD, MH, "form", "Ljava/lang/invoke/LambdaForm;");
        mv.visitInsn(Opcodes.SWAP); // swap form and array; avoid local variable
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, LF, "interpretWithArguments", "([Ljava/lang/Object;)Ljava/lang/Object;");

        // maybe unbox
        Class<?> rtype = invokerType.returnType();
        if (rtype.isPrimitive() && rtype != void.class) {
            emitUnboxing(Wrapper.asWrapperType(rtype));
        }

        // return statement
        emitReturnInsn(rtype);

        classFileEpilogue();
        bogusMethod(invokerType);

        final byte[] classFile = cw.toByteArray();
        maybeDump(className, classFile);
        return classFile;
    }

    /**
     * Generate bytecode for a NamedFunction invoker.
     */
    static MemberName generateNamedFunctionInvoker(MethodTypeForm typeForm) {
        MethodType invokerType = LambdaForm.NamedFunction.INVOKER_METHOD_TYPE;
        String invokerName = basicTypeCharSignature("invoke_", typeForm.erasedType());
        InvokerBytecodeGenerator g = new InvokerBytecodeGenerator("NFI", invokerName, invokerType);
        return g.loadMethod(g.generateNamedFunctionInvokerImpl(typeForm));
    }

    static int nfi = 0;

    private byte[] generateNamedFunctionInvokerImpl(MethodTypeForm typeForm) {
        MethodType dstType = typeForm.erasedType();
        classFilePrologue();

        // Suppress this method in backtraces displayed to the user.
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);

        // Force inlining of this invoker method.
        mv.visitAnnotation("Ljava/lang/invoke/ForceInline;", true);

        // Load receiver
        emitAloadInsn(0);

        // Load arguments from array
        for (int i = 0; i < dstType.parameterCount(); i++) {
            emitAloadInsn(1);
            emitIconstInsn(i);
            mv.visitInsn(Opcodes.AALOAD);

            // Maybe unbox
            Class<?> dptype = dstType.parameterType(i);
            if (dptype.isPrimitive()) {
                Class<?> sptype = dstType.basicType().wrap().parameterType(i);
                Wrapper dstWrapper = Wrapper.forBasicType(dptype);
                Wrapper srcWrapper = dstWrapper.isSubwordOrInt() ? Wrapper.INT : dstWrapper; // narrow subword from int
                emitUnboxing(srcWrapper.wrapperType());
                emitPrimCast(srcWrapper.basicTypeChar(), dstWrapper.basicTypeChar());
            }
        }

        // Invoke
        String targetDesc = dstType.basicType().toMethodDescriptorString();
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, MH, "invokeBasic", targetDesc);

        // Box primitive types
        Class<?> rtype = dstType.returnType();
        if (rtype != void.class && rtype.isPrimitive()) {
            Wrapper srcWrapper = Wrapper.forBasicType(rtype);
            Wrapper dstWrapper = srcWrapper.isSubwordOrInt() ? Wrapper.INT : srcWrapper; // widen subword to int
            // boolean casts not allowed
            emitPrimCast(srcWrapper.basicTypeChar(), dstWrapper.basicTypeChar());
            emitBoxing(dstWrapper.primitiveType());
        }

        // If the return type is void we return a null reference.
        if (rtype == void.class) {
            mv.visitInsn(Opcodes.ACONST_NULL);
        }
        emitReturnInsn(Object.class); // NOTE: NamedFunction invokers always return a reference value.

        classFileEpilogue();
        bogusMethod(dstType);

        final byte[] classFile = cw.toByteArray();
        maybeDump(className, classFile);
        return classFile;
    }

    /**
     * Emit a bogus method that just loads some string constants. This is to get the constants into the constant pool
     * for debugging purposes.
     */
    private void bogusMethod(Object... os) {
        if (DUMP_CLASS_FILES) {
            mv = cw.visitMethod(Opcodes.ACC_STATIC, "dummy", "()V", null, null);
            for (Object o : os) {
                mv.visitLdcInsn(o.toString());
                mv.visitInsn(Opcodes.POP);
            }
            mv.visitInsn(Opcodes.RETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();
        }
    }
}
